This invention relates to an aluminum nitride-based sintered body with high thermal conductivity and, more particularly, to an aluminum nitride-based sintered body of high thermal conductivity adapted, for example, as a high heat dissipating substrate for a semiconductor device.
Aluminum nitride (AlN) has high mechanical strength in a wide temperature range and has excellent chemical stability. Therefore, the AlN has been applied as refractory material and can be applicable as a heat dissipating substrate for a semiconductor device by using its high thermal conductivity and high electric insulating property and so on. Since the AlN generally has no melting point and decomposes at a higher temperature than 2200.degree. C., the AlN is normally used in the sintered form.
The AlN-based sintered body is commonly manufactured by the pressureless sintering method or hot pressing method. The pressureless sintering process comprises the steps of mixing the AlN raw powder with a sintering aid such as a rare earth compound, for example, yttrium, or a material containing a rare earth element such as yttrium oxide, molding the raw mixture, and finally sintering the molded body. However, the AlN-based sintered body manufactured by the above-mentioned conventional process has a lower thermal conductivity than the theoretical thermal conductivity (about 320 W/m.multidot.K) of AlN.
The hot pressing method to carried out by using the AlN powder alone or a raw material prepared by adding the above-mentioned sintering aid to the AlN powder. It is very difficult to manufacture a intricately shaped sintered body by said conventional hot pressing method. The thermal conductivities of an AlN-based sintered body obtained by both the atmospheric sintering method and the hot pressing method are still lower than the theoretical value.